Apparatus for grinding one-piece bifocal lenses.



C. C. ALLEN. APPARATUS FQBSRINDING ONE PIECE BIEOCM. LENSES. APPLICATIQN FILED MAY 11. 1914. RENEWED um. 3. 1911.

1,261,674. Patented Apr. 2, 1918.

3 SHEETS-SHEET I- JmwnZEh k C1666 Gdllen.

C. C. ALLEN.

APPARATUS FOR GRINDING ONE PIECE BIFOCAL LENSES.

APPLICATION FILED MAYII, I914. RENEWED IAN. 8. l9l7.

Patented Apr. 2, 191&

3 SHEETS-SHEET 2- Z czzze Civilian.

(raven/Em C. C. ALLEN. APPARATUSFOR GRINDING ONEHECE BIFOCAL LENSES LICATION mzo MAYII 1914 RENEWED IAN APPV .a.|9|1. 1,261,674. Patented Apr. 2,1918.

3 EEEEEEEEEEEE 3- CLILE c. ALLEN, or cnrcaoo, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, 'ro NEW YORK LENSCOMPANY, me, or NEW YORK, N. Y., A CORPORATION on NEW YORK.

APPARATUS FOR GRINDING ONE-PIECE IBIFOCAL LENSES.

Specification of Letters Patent.

Patented Apr. 2, 191 8.

Application filed May 11, 1914, Serial No. 837,935. Renewed January 8; 1917. Serial No. 141,389.

' 'To all whom it may concern:

I which the following is a specification.

- avoidin The present invention has reference to certain improvements in apparatus for rinding lenses, and particularly'bi-focal fianses, in which the reading and distance fields are formed in the same one-piece lens crystal. The invention has reference more particularl lenses of t is type in which the surfaces of the reading and distance fields are concentricall ground.

In t is class of work, it is very important that the apparatus should be of such construction that the two fields may be so ground as to bring their line of'joinder into a surface"common to both fields, thereby any shoulder or step at the line of join er of the two fields. In order that this result may be obtained with nicety and certainty, the apparatus must be so constructed and operated that assurance may be had that the two fields' are, in fact, concentrically ground-that is, ground in such a way that the centers of the spheres, on which they are ground, lie on the same radial line. Unless this precaution be taken in the construction and operation of the apparatus, it will be found when the two fields are completed that they are tilted or tipped with respect to each other, so that on one portion of the line of joinder there with be a shoulder facing the readin field, whereas on another portion of theline of joinder ghege will be a shoulder facing the distance In the pastit has been the main aim of inventor working in this art to try and produce an apparatus of such construction that the two fields can be concentrically ground at the same time or simultaneously. When the fields are to be simultaneously ground, the apparatus must be very nicely and accurately constructed and operated in order to cause the crystal to rotate always with the center of its radius of generation at the same point in space. Unless the apparatus be thus constructed, the center of the radius of generation will move around to an apparatus for grindingas the crystal rotates, and. consequently the crystal will wabble during its rotation. Inasmuch as the two grinding laps are simultaneously in operation, and are grinding the crystal on both sides of the center line simultaneously, and inasmuch as these laps are substantially stationary, it will be found that the two fields will be tilted in the objectionable manner above mentioned when the crystal is complete.

I have discovered that, if the two fields be individually ground, each lap may rise and fall periodically with the rotation of the crystal in order to compensate for the wabblin of the crystal, as it is found to be practically impossible to always replace the crystal on the spindle head or holder in the same position with respect to the axis of rotation, so that the field which is being operated on will be perfectly ground concentrically with the radius of the circle on which the crystal rotates, notwithstanding any slight wabbling motion. If then the other surface beafterward ground, the lap used in such second grinding operation will likewise be able to continuously adjust itself during the rotation of the crystal, so that the surface of such second field will also be concentric with the axis on which the crystal rotates, and thus in the end both fields will be correctly ground. In order,

however, that this individual grinding proc- I ess may be successfully practised, it is de sirable, if not imperative, that the apparatus should be so constructed that the two grinding operations may properly controlled. This control includes a proper centering of the grinding laps with respect to the axis of crystal rotation, as well as a control of the eccentricity of movemeint or vibration of the laps, for the purpose of properly centering the laps with respect to the center of c stal rotation during their oscillation or vi ration.

tion and combinations of parts hereinafter described and. claimed.

In the drawings-- Figure 1 shows a side elevation of one form of apparatus for carrying into practice the features of the present invention;

Fig. 2 shows a plan View of the mechanism shown in Fig. 1;

Fig. 3 is a horizontal section through the turn buckle;

Fig. 4 is a detailed vertical section through one of the lap pressure-pins;

. Fig. 5 is a cross section through an unground crystal;

Fig. 6 is a cross section through the crystal after the completion of the read ng field;

Fig. 7 is a cross section through the crystal after the completion of the distance field; and

Fig. 8 is an enlarged detail of a portion of the crystal of Fig. 7, showing how the grinding lap may be caused to provide a substantially perfect line of joinder between the two fields by carrying forward the grinding and polishing operations individually instead of simultaneously.

Fig. 9 is a vertical section taken on line 9-9 of Fig. 2 looking in the direction of the arrows.

In Figs. 1 to 4:, inclusive, I have shown one construction of mechanism which embodies the features of my invention, while in Figs. 5 to 8, inclusive, I have shown one series of steps or operations on the crystal by means of which my individual field grinding process may be carried into efl'ect.

In the construction shown in Figs. 1 to 4, inclusive, there is provided a crystal-carrying head 9 and an oscillatable head 10. The head 9 is carried by 'a vertical spindle 11,

which may be rotated rapidly in any de-' sired manner. The head'lO carries two or more lap centering pins 12 by means of which the particular lap or laps in service are held in operative engagement with the crystal. In the particular arrangement illustrated in the several figures there are two.

of these pins, a central one for the lap which grinds the reading field and a side one for the lap which grinds the distance field. The laps may be of any one of a number of familiar forms, -as, for example, that form in which the lap1 is provided on its upper surface with a lug aving a slight depression or socket to receive the point of the pin.

Assuming that the individual field grinding process is to be practised by grinding the reading field first, a lap having the desired curvature and of the desired size would be placed on the crystal (the crystal having first been secured to the head 9 in a usual manner), and then the grinding operation would be commenced and allowed to continue until the reading field had been mac ete ground down the desired amount, as shown at 13 in Fig. 6. After the reading field had thus been ground down, the read-mg grind-.

ing lap would be removed, and then the field 13 would be polished in any desired manner.

had been completed that there remained a small rounded portion 14: around the edge or periphery of the shoulder, as shown greatly exaggerated in Fig. 8. The grinding of the distance field would then be commenced. In the apparatus illustrated there is provided but a single pin for applying pressure to a single dlstance grinding lap,

and this is the preferred arrangement. I-Iavingapplied the distance grinding lap to the crystal, and having applied pressure to. overlie the shoulder of the reading field a slight amount to insure a proper removal of crystal from the distance field clear up to the reading field. This overlap, however,

.is not objectionable for the reason that, as

the surface of the distance field-approaches that of the reading field, the rounded or curved portion 14 of the shoulder will gradually be wiped out until finally a practically perfect line of joinder is secured between the two fields. After the grinding of the distance field has been completed be polished in order to complete the fourth step in the process of producing the crystal having the two fields individually ground of desired dioptrics. may be cut into two parts for the production of a pair of lenses in the usual manner.

In case it be desired to grind the distance field first, this may be done, in which case the lap used in grinding the reading field would afterward would be manipulated in such a manner as will presently appear to completely eliminate the shoulder between the fields so as to produce a substantially perfect lens after the several grinding and polishing operations on the upper end of a rock arm 18, which is pivoted to a stationary pivot 19, so that the yoke may rock with a straight back and e chosen of such a size and this field may Thereafter the crystal v 70, It would be found after these operations forth movement in order to carry the grinding la which is in operation through the desire amount of back and forth movement.

At the same time the arm 18 is broad enough, and its pivotal points 19 are suificiently far apart, to prevent any sidewise or twisting movement of the head 10.

In the rear portion of the a paratus there is provided a vertical. spin e 20, having on its u per end a head 21. An eccentrlc plate22 is pivoted to the head 21 at the point 23, its other end being provided with a slot to receive a pin or set screw 24:. By means of this in and slot connection the plate 22 may be ocked in any desired position on the head 21. The plate 22 in turn carries a crank pin 23 on which ridesthe collar 24". A yoke 25 is pivoted to the collar 2 1 by means of the pins 26, so that said yoke Wlll be driven back and forth to a distance depending upon the amount of eccentricity created by the plate 22. The yoke 25 connects to the yoke 16 by means of a yoke 26 and a turn buckle 27. This turn buckle is for the purpose of adjusting the distance between the yokes 25 and 26, so that the extreme forward and backward limits of movement of the head 10 can be controlled. As a convenient construction of turn buckle, I have shown the yokes 25 and 26* as being provided with the lugs 27 and 28, which are threaded to receive the ends of the turn buckle pin. 7 These threads are formed in reverse directions, so that the mere turning of the lugs 27 and 28 as being split, and as carrying sleeves 29 provided with set-screws 30, so'that the lugs 27 and 28 can be clamped onto the ends of the turn buckle pin after the desired adjustment has been secured, in, order to prevent any disarrangement.

This turn buckle construction illustrates one means or construction for controlling the forward and backward limits of throw of the head 10. Such a construction is desirable for the purpose of insuring an equal throw of the grinding laps to both sides of the center of rotation of the crystal. This will insure an equal amount of grinding action on all portions of the crystal subjected tothe action of the lap. The adjustable eccentric plate 22 permits the degree or extent of eccentricity to be regulated or varied. It will be evident that the total diameter or size of the near or reading field will be equal to the diameter of the lap used in grinding it, plus the total amount of throw measured in a back and forth direction. Therefore, the eccentricity adjustment permits adjustment of the diameter of this field when using a given size of lap, and in like manner permits the eccentricity to be adjusted according to the requirements or desirability as determined by the particular lap which trolling the amount. of eccentricity, but also have combined with this means for accurately adjusting the back and forth throw, so that it will be equal on both sides of the center of rotation.

In Fi 4 I have shown more in detail one form of pin for pressing a lap down into contact with the crystal. In the construction. illustrated, the pin 12 is slidably mounted within a sleeve 31. The pin is provided with a channeled portion 32 adapted to receive a screw or pin 33 which will hmit the downward movement of the pin 12. The upper end of the pin 12 carr'es a stop or abutment 34, and a spring exerts an expanding force tending to raise the pin 12 with respect to the sleeve 31. A screw cap 36 is threaded onto the upper end of the sleeve 31, and limits the upward movement of the pin 12, so that the elevation of said pin can be accurately adjusted by means of this screw cap. The screw cap, if desired, may be provided with a scaled outer surface 37, whereby it may be set into different predetermined positions, thereby enabling the operator to bring the cap and the pin into any desired predetermined position. The sleeve 31 lies beneath 38 in Fig. 2. It may be rigidly connected to the head 10, so that when said head is thrown into the horizontal position illustrated in Fig. 1 the weight of the head will be transmitted down through the pin and onto the grinding or polishin lap. On the other hand, the sleeve 31-for t e distance field lies beneath 39 in Fig. 2. This sleeve is preferably carried by an arm 40 pivoted to the head 10 at the point 41, and provided at its front end with a slot 42 adapted to receive a set screw 43. The sleeve 31 itself projects down through a slot 4.4 of the head. It will thus appear that by rocking the arm 40 back and forth the pin 12 and the lap for grinding the distance field can be set the desired distance to one side of the center of rotation of the lens holder. In this way it is possible to very nicely and accurately adjust the lap for grinding the distance field so as to secure exactly the desired overlap such as is illustrated in Fig. 8, and for other purposes.

Assuming that the sleeves 36 stand in a given position, the head 10 will assume a definite angle when the proper pin 12 is resting on the lap which is to be used. If the'crystal be thick, or if the lap be thicker than usual, the head 10 will not set as far down as would otherwise be the case, andshould bear down exactly parallel to the axis of rotation, both for the purpose of securing a more eflicient and perfect pressure I an equal uickly release v and at the same time giving the operator on the lap travel of the lap both sides of the center; The threaded heads 36 provide a simple means for setting the pins 12 up or down into the desired positions, so that the head 10 will assume a position at right angles to the axis of rotatlon.

The head 10 may be easlly thrown or turned up into the position shown at 17 in Fig. 1, thereby permitting the operator to t e pressure from the laps,

belt 46 onto and off from the fast and loose pulleys simultaneously controls the rotation of both of the spindles.

I wish to point out that it is extremely desirable, in order to produce an optically perfect lens, to grind the fields separately and not simultaneously, and to allow the lap which is used in the second grinding operation to overlap the field which is first ground a slight distance so as to completely eliminate or wipe out the shoulder at the line of joinder between the fields.

While I have herein shown and described only a single form of apparatus embodying the features of my invention, still it will be apparent to those skilled in the art that many other arrangements or embodiments might be devised which would still be within the scope of my invention. Therefore, I do not limit .myself to the arrangement illustrated and described except as I may do so in the claims, but I contemplate within the scope of my invention any equivalent mechanism operating in equivalent manners to produce equivalent results.

I claim:

1. In a lens grinding machine the combination with an upright spindle, and a crystal carrying head on its upper end, of another. upright spindle, an eccentric pin on its upper end, means for adjusting the degree of eccentricity of said pin, a rock arm, a yoke pivotally connected to the upper end of the same, an adjustable connection between the eccentric pin and the yoke, an oscillatable head pivotally connected to the yoke, a centering pin carried by the yoke at a point centrally above the center portion of the crystal carrying head, means for adjusting the centering pin in and out with respect and for the purpose of insuring 'by adjust the amount of projection of said eccentric pin with respect to its spindle, a

49 which drives backwardthrough i the. rock arm to the eccentric pin, means for adjusting the length of said driving conneceonora to the oscillatable head to adjust the amount of extension of the centering pin therefrom, there being a slot in the osclllatable head, an arm" swingingly mounted on the oscillatable head, a centering pin carried thereby, said centering pin extending through the slot aforesaid, means for locking the swing- 4 ing arm in any desired position, and means for adjusting said centerin pin in and out with respect to the oscillata 1e head to theregeniaering pin with respect to the oscillatable 2. In a lens grinding machine the combination with a spindle having on its upper end a crystal carrying head, ofanother spindle, an eccentric pin connected to the upper end of said last named spindle, means for adjusting the degree of eccentricity of said ,85 rock arm swingingly connected to a stationary part, an oscillatable head pivotally connected to the upper end of said rock arm,

a driving connection from the upper end of tion, a centering pin connected to the oscillatable head at a point centrally above the crystal carrying head, means for adjusting said centering pin in and out with respect to the oscillatable head to thereby adjust the amount of extension of said centering pin beyond the oscillatable head, there being a slot in the oscillatable head, an arm pivotally connected to the oscillatable head, a centering pin carried by said arm and extending through the slot, and means for adjusting the amount of projection of said centering pin beyond the oscillatable head.

3. In a lens grinding apparatus the combination with a rotatable spindle having on its upper end a crystal carrying head, of another spindle, an eccentric pin carried thereby, means for-adjusting the amount of eccentricity of said pin, a rock arm swingingly connected to a stationary part, an oscillat; able head pivotally connected to the upper end of said rock arm, an adjustable connection between the upper end of the rock arm and the eccentric pin, a centering pin carried by the oscillatable head centrally above the crystal carrying head, another centering pin connected to the oscillatablehead at a point to one'side of the first mentioned centering pin, both of said centering pins projecting beyond a surface of the oscillatable head andtoward the crystal carrying head, and means for adjusting the extent of such projection of each centering pin.

4. In a lens grinding apparatus the combination with a rotatable spindle having a crystal carrying head on its upper end, of another spindle, an eccentric pin connected to its upper end, a rock arm swingingly connected to a stationary part, a connection be- 1-3( adjusting the amount of such extension of each centering pin.

5. In a lens grinding apparatus the combination with a rotatable spindle having a crystal carrying head, of another spindle, an eccentric pin connected thereto, a rock arm swingingly connected to a stationary part, a connection from the upper end of the rock arm to the eccentric pin, means for V accurately adjusting the length of said conbination with a rotatable spindle having a crystal carrying head connected thereto, of another spindle, an eccentric pin connected thereto, an oscillatable head pivotally connected to a reciprocable part, and a con-.

nection from the reciprocable part to the eccentric pin, means for accurately adjusting the length of said connection, a centering pin carried by the oscillatable head centrally above the crystal carrying head, an-,

other centering pin carried by the oscillatable head above the crystal carrying head and to one side of the first mentioned centering pin, both of said centering pins extending below the surface of the oscillatable head, and means for individually adjusting the amount of such extension of each centering'pin.

7. In a lens grinding apparatus the combination with a rotatable spindle having a crystal carrying head connected thereto of another spindle, an eccentric pin connected thereto, a reciprocable part, a connection between the reciprocable part and the eccen- 6. In a lens grinding apparatus the comtric pin, means for accurately adjusting the length of said connection, means for adjusting the degree of eccentricity of the eccentric pin, an oscillatable head pivotally connected to the reciprocable part, a centering pin carried by the oscillatable head centrally above the crystal carrying head, another centering pin carried by the oscillatable head above the crystal carrying head and to one side of the first mentioned centering pin, both of said centering pins projecting below the lower surface of the oscillatable head, and means for individually adjusting the amount of such extension of each centering pin.

8. In a lens grinding apparatus the combination with a rotatable spindle havin a crystal carrying head, of another spindle, an eccentric member connected thereto, a reciprocable member, a connection from the 'eccentric member to the reciprocable member, an oscillatable head pivotally connected to the reciprocable member, a centering pin carried by the oscillatable head at a point centrally above the crystal carrying head, another centering pin carried by the oscillatable head above the crystal carrying head and to one side of the first mentioned centering pin, both of said centering pins projecting beyond the lower surface of the oscillatable head, and means for individually adjusting the amount of such extension of each centering pin.

9. In a lens grinding apparatus the combination with a rotatable spindle having a crystal carrying head connected thereto, of another spindle, an eccentric member connected thereto, a reciprocable member, a connection from the reciprocable member to the eccentric member, means for accurately adjusting the length of said connection, an oscillatable head pivotally connected to the reciprocable member, means .for adjusting the amount of eccentricity of the eccentric member, a centeringpin carried by the oscillatable head centrally above the crystal carrying head, another centering p1n carried by the oscillatable head above the crystal carrying head and to one side of the first mentioned centering pin,- both of said centering pins extendin beyond the oscillatable head and towar the crystal carrying head, and means for individually adjusting the amount of such extension of each centering pin.

CLILE C. ALLEN. Witnesses:

T. A. BANNING, Jr. Ermuum BANKING. 

